This invention relates to a method for reducing tungsten and derivatives thereof in a glass container and to a glass container with reduced tungsten and derivatives thereof.
Tungsten and derivatives thereof have been commonly used in glass forming techniques. In particular, tungsten-containing pins have been used in forming shaped apertures or channels in glass structures. As used herein, the term “tungsten-containing” means tungsten, tungsten plus one or more other materials, or one or more other materials plus tungsten, in any combination and percentage. Tungsten has a high fusion temperature relative to glass and is well suited for glass manufacturing. Typically, a tungsten-containing pin is used to form an aperture or channel in a glass container, with the glass being thermally and/or mechanically manipulated about the pin and into conforming engagement therewith. An iterative process can be used where a plurality of pins are used sequentially to gradually form the aperture or channel in a sequence of manipulations to the glass. With removal of the final pin, a finished aperture or channel is left in the glass structure. This technique has been commonly used in the formation of glass medical containers, including glass syringe barrels, glass vials, and glass drug cartridge bodies. Each of the glass medical containers (glass syringe barrels, glass vials and glass drug cartridge bodies) includes a reservoir for containing a drug, and a channel in communication with the reservoir to provide a means of accessing or removing the drug from the reservoir, typically via a cannula or similar liquid communication means.
It has been found that tungsten-containing pins undesirably leave a tungsten-containing residue on the formed glass structures, particularly, portions that had been in contact with the pins, for example, the aperture or channel. The tungsten-containing residue may have detrimental effects on any substance contained or stored within the glass medical container. First, tungsten or derivatives thereof may be deposited as particulate matter on an inner surface of the aperture or channel, and such particulate matter may be visible in the contained substance. Certain medical procedures require a medical practitioner to view the procedure under magnification, including the administration of a drug from a glass medical container. The presence of such particulate matter may be dangerous to the patient and may also be disconcerting to the medical practitioner. Second, drugs containing proteins may be adversely affected by exposure to the tungsten or derivatives thereof. Certain proteins are prone to clump or aggregate about tungsten or derivatives thereof. This clumping or aggregation may lead to a loss in efficacy or other undesirable effects of the drug. In addition, in certain situations, the clumping or aggregation may be so extreme that solid fragments may be seen by the naked eye and be disconcerting to a potential user.
Water washing glass medical containers is known in the prior art. Such washing techniques have been known to reduce or remove tungsten-containing residue. However, washing techniques have inherent limitations and cannot reliably and repeatedly remove all or substantially all tungsten and derivatives thereof from a glass medical container.